Available theories suggest that a malfunction of monoamine systems is an essential feature in the cause of schizophrenia and depression. The present objective is to better understand the mechanism of action of neuroleptics and antidepressants on various central DA, NA, A and 5-HT pathways. Such information could lead to the development of new and better drugs against schizophrenia and depression. The present research offers a unique way for studies of this type by combining biochemical and functional studies of DA, NA, A and 5-HT with semiquantitative and quantitative amine fluorescence histochemistry and immunohistochemistry of CA synthesizing ennzymes. In this way a proper regional analysis of monoamine cell bodies and terminals can be otained. It should also be underlined that the present program offers a unique possibility to study the pharmacology of the adrenaline pathways discovered in our laboratory by means of PNMT immunofluorescence, and of the DA nerve terminals in the limbic cortex.